1. Field of the Invention
The present invention relates to polyamide resin-based printing compositions, and in particular to printing compositions useful for hot-melt printing inks.
2. Brief Description of the Prior Art
Ink-jet printing is a non-contact printing process for the printing of many substrates such as paper, films, foils and the like. Certain ink-jet printers are designed to use hot-melt, also known as "phase-change," inks. One requirement of a hot-melt ink is that it be in the solid form at room temperature and in the liquid form when contacted with the elevated operating temperatures maintained in the printhead of a printer employing hot-melt inks. In printing that employs hot-melt inks, molten ink is ejected from the printhead and upon hitting the substrate, cools, and solidifies, and adheres to the substrate.
Hot-melt inks and components for hot-melt inks are disclosed, for example in U.S. Pat. No. 3,653,932, which teaches the use of didodecyl sebacate as a carrier for the ink.
U.S. Pat. No. 4,830,671 to Frihart et. al. discloses a composition for use in hot-melt ink-jet printing applications. The ink comprises a colorant and a resinous binder prepared from polymerized fatty acid, a diamine and a monocarboxylic acid.
U.S. Pat. No. 4,889,650 to Jaeger et. al. also relates to a hot-melt printing composition. The Jaeger ink comprises a colorant and a mixture of two fatty amide materials in which the fatty amide materials are comprised of a tetraamide compound and a monoamide compound. The Jaeger ink is capable of producing thin films of uniform thickness with a high degree of lightness and chroma and which are rectilinearly light transmissive.
U.S. Pat. No. 5,085,099 also to Jaeger et. al. discloses modified hot-melt ink compatible colorants which are comprised of a hot-melt ink-soluble complex of a tertiary alkyl primary amine and dye chromophores. The dye chromophores are materials with at least one pendant acid group in the free acid form and which absorb light in the visible wavelength region to produce color. The composition also contains fatty amide containing material comprised of a dimer acid linked tetraamide and optionally, a monoamide.
The great proportion of the amide resin prior art, and all of the art disclosed to be useful for hot-melt ink applications, teaches the preparation and use of monocarboxylic acid-terminated resins. Nowhere is monoamine termination taught as useful for hot-melt ink use.
A number of patents in the prior art, including U.S. Pat. Nos. 4,297,479; 4,684,409; 4,308,374; and 4,389,521, disclose the production of high molecular weight polyamides from equimolar amounts of diamine and diacid. These polyamides possess film-forming characteristics and are useful in the production of nylon.
U.S. Pat. No. 4,066,585 discloses polyamide resins suitable for use in hot-melt flexographic and intaglio inks comprising polymerized fatty acid, a monocarboxylic acid and a diamine or alkanolamine.
U.S. Pat. No. 3,595,816 to Barrett discloses adhesive polyamide compositions in which hydrogenated dimer acid is reacted with amine, wherein from 90-100 equivalent percent of the amine should be diamine. The remainder of the amine may optionally include monoamine.
U.S. Pat. No. 4,816,549 to Rumack discloses a polyamide resin composition which is made up of from 5-35 equivalent percent of a monoamine, 65-95 equivalent percent of a diamine (some of which must be 1,2-diaminocyclohexane), 75- 100 equivalent percent of a diacid formed from polymerizing fatty acids, and 0-25 equivalent percent of an aliphatic or cycloaliphatic diacid. The monoamine terminated compositions are disclosed as being useful as binders in solution printing inks because they are soluble in toluene.
U.S. Pat. No. 2,272,466 discloses a process for the preparation of polyamides or, more specifically, diamides. The process comprises condensing a selected primary or secondary amine with a cyclic dicarboxylic acid such as terephthalic acid or isophthalic acid, where the dicarboxylic acid is characterized as being unable to form an intramolecular anhydride linkage.
There continues to exist a need in the art for hot-melt ink components having the proper combination of melting point, melt viscosity, clarity, inertness, compatibility with other components, and adhesive properties which meet the commercial demands placed on these materials, especially for printing on non-porous substrates such as polyethylene, polyesters and polystyrene films.